"Health-Related Quality of Life in Operated Adult Patients with Tetralogy of Fallot and Correlation with Advanced Imaging Indexes and Cardiopulmonary Exercise Test" A Narrative Review.

Congenital heart diseases (CHD) are considered to be the second leading cause of death during infancy and childhood. However, due to advanced imaging techniques, more than 90% of children with complex CHD survive into adulthood, increasing the prevalence of CHD in the population. Tetralogy of Fallot (ToF) is considered to be the most common, complex, cyanotic CHD. Health is an important determinant of a patient's quality of life and this drove physicians to examine ToF patient's health related quality of life (HRQOL), in order to improve medical and surgical interventions. The purpose of this narrative review was to identify parameters derived through modalities, such as cardiovascular magnetic resonance, echocardiography and cardiopulmonary exercise testing and correlate them with repaired ToF (rToF) patient's perceived HRQOL. It is widely proven that rToF patients have worse physical capabilities than healthy population and this can be safely attributed to their cardiac condition. Unfortunately, rToF population is relatively small, making most of the included trials reliable and unable to uniformly agree to the same results. Further investigation is mandatory in order to discover those parameters that will allow physicians to better understand HRQOL in this population, leading to better medical management and rehabilitation.

The value of myocardial strain imaging in the evaluation of patients with repaired Tetralogy of Fallot: a review of the literature.

Tetralogy of Fallot (ToF) is considered to be the most common, complex, cyanotic congenital heart disease (CHD) representing 7-10% of all congenital heart defects, whereas the patients with ToF are the most frequently operated in their early infancy or childhood. Cardiac magnetic resonance (CMR) consists a valuable imaging technique for the diagnosis and serial follow-up of CHD patients. Furthermore, in recent years, advanced echocardiography imaging techniques have come to the fore, aiming to achieve a complete and more accurate evaluation of cardiac function using speckle tracking imaging modalities. We conducted a review of the literature in order to assess the myocardial deformation of patients with repaired ToF (rToF) using echocardiographic and CMR parameters. Patients with rToF have impaired myocardial strain parameters, that are well standardized either with the use of speckle tracking echocardiography or with the use of CMR imaging. Subclinical left ventricular dysfunction (low GLS) and myocardial dyssynchrony are commonly identified in rToF patients. Impaired left atrium (LA) and right atrium (RA) mechanics are, also, a common finding in this study population, but the studies using atrial strain are a lot fewer than those with LV and RV strain. No studies using myocardial work were identified in the literature, as far as rToF patients are concerned, which makes it an ideal field for further investigation.

The utility of splenic imaging parameters in cardiac magnetic resonance for the diagnosis of immunoglobulin light-chain amyloidosis.

OBJECTIVES: Cardiac magnetic resonance (CMR) imaging is a key test in the diagnosis of cardiac amyloidosis (CA). Extracardiac involvement is common in light chain (AL) amyloidosis and MRI findings may assist in its diagnosis. We sought to investigate the utility of splenic CMR parameters for the diagnosis of CA. METHODS: Thirty-four patients with AL amyloidosis and 32 patients with severe left ventricular hypertrophy in the setting of aortic stenosis (LVH-AS) who completed 3T cardiac MRI at the time of their diagnosis of AL or LVH-AS were assessed with T1, T2 (modified Look-Locker inversion recovery), extracellular volume (ECV) mapping, and late gadolinium enhancement (LGE) imaging of the heart and spleen. RESULTS: Age, left ventricular mass index, wall thickness, ejection fraction, and splenic dimensions did not differ significantly between groups. All AL patients had cardiac involvement. T1 and T2 spleen mapping did not differ significantly between groups but AL patients had higher median ECV in the spleen than in LVH-AS (AL 46.9%, LVH-AS: 31%, p < 0.001), and significantly lower short tau inversion recovery ratio (AL: 1.7, LVH-AS: 2.7, p < 0.001) both with very good diagnostic performance to diagnose AL. We identified 16 AL patients with spleen involvement and 16 without. Spleen ECV and "normalized" spleen ratio, defined as the ratio of spleen LGE to muscle values exhibited strong correlation and had excellent diagnostic performance to discriminate those with spleen involvement. CONCLUSION: Our findings show that spleen CMR parameters can identify spleen involvement in AL patients and differentiate them from those without AL amyloidosis.

Peripheral blood natural killer cells in sarcoidosis are associated with early cardiac involvement.

AIM: To evaluate the distribution of circulating immune cell subsets in peripheral blood of patients with sarcoidosis and investigate if there is an association with an underlying cardiac involvement. METHODS AND RESULTS: Eighty-five newly diagnosed treatment-naïve patients with sarcoidosis (50 women) were included in the study. All patients underwent a thorough cardiac investigation, including cardiac magnetic resonance imaging (CMR). Of all patients, 19 (23.53%) had myocardial involvement, and the NK subpopulation in these patients in peripheral blood was significantly decreased compared to patients without (n = 63, p = 0.001 and p = 0.003 respectively). The absolute number of NKT cells (CD3+CD16/56+ ) in patients with cardiac involvement was highly correlated with T2 map increased values in MRI (r = -686, p = 0.041) showing that low NKT cell count correlates with the inflammatory process of the heart. No difference in CD19, CD3, CD4, CD8 and CD3- NK cell counts was found between groups. Lung severity was not found to correlate with the number of NK cells. CONCLUSION: We found that low NK cell count in peripheral blood of patients with sarcoidosis is associated with cardiac involvement, and the number of NK-T cells correlates with CMR findings indicative of myocardial inflammation. This finding might have a potential clinical application in detecting clinically silent cardiac involvement in sarcoidosis and may also suggest potential targets for therapeutic interventions.

Diagnostic accuracy of two-dimensional shear wave elastography in detecting hepatic fibrosis in children with autoimmune hepatitis, biliary atresia and other chronic liver diseases.

BACKGROUND: Although fibrosis is the main determinant of liver stiffness, other disease-related factors usually disregarded in studies on liver elastography, such as inflammation and cholestasis, may influence liver stiffness. OBJECTIVE: To evaluate the accuracy of two-dimensional (2-D) shear wave elastography in assessing liver fibrosis in children with chronic liver disease by controlling for the confounding role of several disease- and patient-related factors. MATERIALS AND METHODS: Three disease groups were studied: 1) various chronic liver diseases, 2) autoimmune hepatitis and 3) biliary atresia. The METAVIR (meta-analysis of histological data in viral hepatitis) score was used for fibrosis staging and grading of necroinflammatory activity. Multiple linear regression was used to evaluate the relationship between liver stiffness measurements and disease-related factors. The diagnostic accuracy of elastography for predicting fibrosis stages was assessed by calculating the area under the receiver operating characteristic curves. RESULTS: The various chronic liver diseases group (n=32; 7.1±4.9 [mean±standard deviation] years) showed liver stiffness of 8.9±5.0 (mean±standard deviation) kPa, the autoimmune hepatitis group (n=33; 8.1±4.4 years) of 7.1±2.7 kPa, and the biliary atresia group (n=19; 0.2±0.1 years) of 19.7±15.2 kPa. Liver stiffness measurements differed across METAVIR fibrosis categories in all disease groups. The highest values were found in biliary atresia, at fibrosis stages ≥F2 (F2: 12.4±1.6 kPa, F3: 17.8±2 kPa, F4: 41.5±12.4 kPa). Liver stiffness was strongly associated only with fibrosis (P<0.0001) in various chronic liver diseases, but with necroinflammatory activity (P<0.0001) and fibrosis (P=0.002) in autoimmune hepatitis, and with age (P<0.0001), fibrosis (P<0.0001) and cholestasis (P=0.009) in biliary atresia. Optimal cutoffs for detecting advanced fibrosis (≥F3) were 16 kPa (area under curve: 0.98; sensitivity: 87.5%; specificity: 96.7%) in biliary atresia and 8.7 kPa (area under curve: 0.98; sensitivity: 93.8%; specificity: 96.1%) in other chronic liver diseases. CONCLUSION: Two-dimensional shear wave elastography is reliable in assessing liver fibrosis in children with chronic liver diseases.

Prevalence, distribution and clinical significance of joints, muscles and bones in sarcoidosis: an 18F-FDG-PET/CT study.

OBJECTIVES: In Sarcoidosis joints-muscles-bones (JMBs) localizations are of the least common. 18F-FDG-PET/CT imaging revolutionized detection of JMBs involvement by adding metabolic activity information and allowing for a comprehensive, whole-body mapping of the disease. AIM AND METHODS: This study investigated prevalence, distribution, and clinical significance of JMBs sarcoidosis in 195 consecutive patients that underwent 18F-FDG PET/CT examination. RESULTS: Joint and bone involvement were encountered in 15% of patients with a mean of the maximum-standardized-uptake-value (SUVmax) of 6.1. Most common location was the axial skeleton. Hypercalciuria was significantly more frequent in patients with osseous involvement (p = 0.003). Muscle activity (SUVmax = 2.4) was encountered in 20% of the patients, most frequently in treatment-naïve (p = 0.02). The muscles of the lower extremities were affected the most. Muscle and bone localization coexist in 50% of the cases. JMBs disease was almost asymptomatic, not related to chronicity but to pulmonary, nodal, and systemic disease. Long-term follow-up and treatment response of affected patients confirmed sarcoidosis. CONCLUSION: 18F-FDG-PET/CT revealed JMBs localizations and coexistence with other organ sites supporting the concept that sarcoidosis is a systemic disease. By allowing an integrative interpretation of multi-organ involvement in the context of a pattern highly suggestive of sarcoidosis, it strongly keeps-off the diagnosis of malignancy.

Emerging phenotypes of sarcoidosis based on 18F-FDG PET/CT: a hierarchical cluster analysis.

Objectives: In sarcoidosis, the definition of organ involvement with traditional means appears laborious and somewhat controversial, and phenotyping by the above overlapping. 18F-FDG PET/CT defines disease extent by activity more precisely, and may result in a better understanding of sarcoidosis disease behavior and phenotypes expression. We hypothesized that 18F-FDG PET/CT could add in the phenotyping of sarcoidosis patients by unveiling in detail sites of involvement even in clinically and physiologically silent disease.Methods: This study was designed to investigate the role of 18F-FDG PET/CT in phenotyping sarcoidosis using cluster analysis by adding this new means in the routine work-up of 195 sarcoidosis patients of a single academic center.Results: 18F-FDG PET/CT succeeded to identify despite the random distribution of the disease, an ordered stratification into 4 phenotypes: I) thoracic nodal hilar-mediastinal, II) thoracic nodal hilar-mediastinal and lungs, III) an extended thoracic and extra-thoracic only nodal phenotype including inguinal-abdominal-supraclavicular stations, and IV) all the above plus systemic organs and tissues such as muscles-bones-spleen and skin.Conclusion: Though further studies are necessary to confirm findings as patterns of disease behavior; the proposed phenotypes may prove useful in the design of future studies with homogeneous cohorts facilitating in sarcoidosis patients a personalized medicine approach.

18F-FDG PET/CT in Pulmonary Sarcoidosis:Quantifying Inflammation by the TLG index.

Objectives: In sarcoidosis progressive pulmonary disease affects prognosis. Pulmonary disease activity estimated by classic means poorly predicts severity and progressiveness. 18F-fluoro-2-deoxyglucose-positron-emission-tomography computed-tomography (18F-FDG-PET/CT) estimates pulmonary activity by inflammatory-cells metabolism. We aimed to investigate pulmonary sarcoidosis by 18F-FDG-PET/CT and evaluate the role of total-lesion-glycolysis (TLG) value, as an index quantifying the whole burden of lung inflammation.Methods: This is a retrospective study of sequentially gathered data. From a Greek cohort of 195 sarcoidosis-patients, 87 were identified with lung increased 18F-FDG uptake and further studied.Results: Visualizing lung by 18F-FDG-PET/CT identified new imaging patterns and revealed activity in all Scadding stages. Ever-smokers presented significantly higher TLG and lower DLCO compared to never-smokers. However, TLG value did not correlate with functional indices and did not differ between symptomatic and non-symptomatic patients. Among treatment-naïve patients, TLG did not differ significantly in those requiring therapy compared to those remained off.Conclusion: 18F-FDG PET/CT improved imaging and detection of pulmonary involvement and through TLG value revealed the deleterious smoking effect. The fact that TLG neither detected patients with clinical symptoms and functional impairment nor identified those requiring treatment once again confirms that in pulmonary sarcoidosis the link between activity, severity and decision to treat still eludes us.

Cardiovascular imaging approach in pre and postoperative tetralogy of Fallot.

Advances in the medical and surgical management of Tetralogy of Fallot have led to marked increase of the number and age of survivors. Imaging in patients with Tetralogy of Fallot plays a crucial role in the diagnosis and follow up, and essentially guides management and intervention in this entity. This study systematically reviews the imaging modalities used in patients with Tetralogy of Fallot in the evaluation of preoperative and postoperative anatomic and hemodynamic lesions, as well as disease progression in this diagnosis. Various invasive and noninvasive imaging modalities, most commonly echocardiography and cardiovascular magnetic resonance, computed tomography and angiocardiography provide the imaging information required for diagnosis, management and follow up in Tetralogy of Fallot. The choice of the appropriate imaging tool or their combination is guided by the clinical question, the patient's clinical condition and contraindications as well as the strengths and weaknesses of each imaging modality. Tetralogy of Fallot is the most common complex congenital heart disease with long term survivors that need close follow up and complicated management, including multiple surgical and transcatheter interventions. Knowledge of the role and protocols of imaging in Tetralogy of Fallot is extremely important for the clinical as well as the imaging physician in order to optimize patients' management and long-term prognosis.

Proton Density Fat Suppressed MRI in 3T Increases the Sensitivity of Multiple Sclerosis Lesion Detection in the Cervical Spinal Cord.

PURPOSE: Considering the number of multiple sclerosis (MS) patients referred for clinical spinal cord imaging, the optimization of imaging protocols plays a crucial role. We aimed to evaluate the use of proton density (PD) turbo spin-echo (TSE) with spectral attenuated inversion recovery (SPAIR) fat suppression and compare it with the currently recommended T2-TSE-SPAIR in sagittal plane in cervical spinal cord imaging. METHODS: In this study 35 MS patients with clinically suspected or known spinal cord lesions were scanned on a 3.0T magnetic resonance imaging (MRI) system. In addition to the routine protocol, PD-TSE-SPAIR sequences were obtained to quantitatively and qualitatively evaluate lesion detectability and image quality compared to T2-TSE-SPAIR sequences. Quantitative analysis was based on measurements of lesion-to-cord contrast ratio (LCCR), lesion contrast-to-noise ratio (LCNR) and lesion dimensions and the qualitative analysis on ranking with a predetermined score scale. The presence of lesions in these sequences was verified in axial T2 multi-echo gradient echo images. RESULTS: In quantitative analysis, the lesions on PD-TSE-SPAIR had statistically significantly higher contrast (p < 0.05), according to the statistical test of LCCR, LCNR calculated contrast and measured lesion dimensions. Qualitative analyses were congruent with quantitative results; the median rank of PD-TSE-SPAIR was significantly higher than T2-TSE-SPAIR (p < 0.05). Of the 34 detected lesions 9 (26%) were not visualized in T2-TSE-SPAIR sequence. CONCLUSION: Considering its superiority in contrast ratios and lesion dimensions when compared to T2-TSE-SPAIR in both qualitative and quantitative analyses, we therefore recommend PD-TSE-SPAIR as a pivotal sequence to evaluate demyelinating spinal cord lesions at 3T.

Ipsilateral and contralateral cerebro-cerebellar white matter connections: A diffusion tensor imaging study in healthy adults.

BACKGROUND AND PURPOSE: The cerebellum has a pivotal role in regulating human behavior; yet whether this function is mediated only through contralateral cerebro-cerebellar pathways is under-investigated. Thus, we examined feed-backward and feed-forward ipsilateral and contralateral cerebro-cerebellar connections using a detereministic diffusion tensor imaging (DTI) algorithm, the robustness of which was also estimated using phantom DTI data. MATERIALS AND METHODS: Fifty-one healthy controls (22-60 years old; 15 males/36 females) were scanned in a 3T MRI scanner with a 30-direction DTI sequence. Multiple region-of-interest (ROI) method was applied for the reconstruction of the ipsilateral and contralateral (based on cerebellar seed ROI) fronto-ponto-cerebellar (FPC), parieto-ponto-cerebellar (PPC), temporo-ponto-cerebellar (TPC), occipito-ponto-cerebellar (OPC) and dentate-rubro-thalamo-cortical (DRTC) tract bilaterally using the Brainance DTI Suite. A realistic diffusion MR phantom was used to evaluate the fiber tracking methodology for 16 fibers containing crossing, kissing, splitting and bending configurations. RESULTS: Both contralateral and ipsilateral FPC, PPC, OPC and ipsilateral DRTC tracts were successfully reconstructed; the contralateral DRTC tract was not reconstructed in all subjects. Also, the TPC tract was not reproduced in several subjects mostly regarding the contralateral connection. Descriptive DTI measures (number of fibers, fractional anisotropy, radial and axial diffusivity) are presented for each tract. Regarding phantom data, Brainance DTI Suite returned a dataset of 16 fibers that almost perfectly matched the 16 ground truth fibers. CONCLUSIONS: We identified ipsilateral and contralateral connections using a clinically applicable DTI sequence, a robust deterministic algorithm and an unbiased methodology, which can be applied in daily practice in different brain pathologies.

Performance of two--dimensional ultrasound shear wave elastography: reference values of normal liver stiffness in children.

BACKGROUND: Two-dimensional (2-D) shear wave elastography is a new sonographic elastography method for noninvasive measurement of liver stiffness. OBJECTIVE: The aim of this study was to establish reference values of normal liver stiffness on 2-D shear wave elastography in children. MATERIALS AND METHODS: Two-dimensional shear wave elastography values were measured in 202 children with no liver disease from the neonatal period to puberty, who were divided into 4 age groups: newborns and infants, preschoolers, elementary school children and adolescents. We investigated the effects of age, depth of elastography measurement, transducer, number of measurements per child, liver size and Doppler parameters of hepatic blood flow on liver elasticity values. RESULTS: The mean normal liver elasticity value in the study population was: 4.29±0.59  kilopascals (kPa). In neonates and infants, mean liver elasticity value was 4.63 (± 0.6) kPa, in preschoolers and elementary school children, 4.05 (± 0.57) kPa and 4.15 (± 0.52) kPa, respectively, and in adolescents, 4.39 (± 0.55) kPa. Values in neonates and infants as well as adolescents were significantly higher than in preschoolers and elementary school children (Kruskal-Wallis, P<0.001; Mann-Whitney U tests, P<0.05). There was no significant association between liver elasticity values and size of the right lobe or Doppler parameters of hepatic blood flow. Different depths and the number of elastography measurements had no effect on liver elasticity values. CONCLUSION: Two-dimensional shear wave elastography is achievable in a wide range of age in children. We established the reference values of normal liver stiffness on 2-D shear wave elastography in children.

Investigating Gray and White Matter Structural Substrates of Sex Differences in the Narrative Abilities of Healthy Adults.

Linguistic aspects of narration have been investigated in healthy populations, in a wide variety of languages and speech genres with very different results. There is some evidence indicating that linguistic elements, such as speech rate (i.e., the measure indicating the amount of speech produced in a certain time period), mean length of utterance (MLU) (i.e., the index reflecting sentence grammatical structure), frequency of nouns and verbs, might be affected by non-linguistic factors such as sex. On the other hand, despite the existence of neuroimaging evidence of structural differences between males and females, it is yet unknown how such differences could explain between-sex disparities in linguistic abilities in natural speech contexts. To date, no study has evaluated discourse production elements in relation to sex differences and their neural correlates in terms of brain structure, a topic that could provide unique insights on the relationship between language and the brain. The aim of the present study was to determine sex differences in narrative skills in healthy adults and to investigate white and gray matter structural correlates of linguistic skills in each group. Twenty-seven male and 30 female (N = 57) right-handed, neurologically intact, monolingual Greek speakers, matched for age and years of education, participated. Narrations of a personal medical event were elicited. Linguistic elements of speech rate (words per minute), MLUs, frequency of nouns and verbs were calculated for each speech sample, by two independent raters. Structural 3D T1 images were segmented and parcellated using FreeSurfer and whole-brain between-sex differences in cortical thickness, cortical volume and surface area, were obtained. Between-group differences in white matter diffusion tensor scalars were examined via Tract-Based Spatial-Statistics and whole-brain tractography and automated tract delineation using Automated Fiber Quantification. Speech rate and noun frequency were significantly lower for men, while verb frequency was significantly higher for women, but no differences were identified for MLU. Regarding cortical measures, males demonstrated increased volume, surface area and cortical thickness in several bilateral regions, while no voxel-wise or tractography-based between-group differences in white matter metrics were observed. Regarding the relationship between sex and speech variables, hierarchical regression analyses showed that the superior/middle frontal cluster in surface area may serve as a significant predictor of speech rate variance, but only in females. We discuss several possible interpretations of how sex-related speech abilities could be represented differently in men and women in gray matter structures within the broad language network.

Functional MRI Study to Examine Possible Emotional Connectedness in Identical Twins: A Case Study.

In the present case study, we investigated possible emotional connectedness between monozygotic twins by means of functional magnetic resonance imaging (fMRI). During the experimental condition, Twin 2 was randomly selected to participate in the neuroimaging protocol while Twin 1 participated in the experimental condition outside the MRI scanner (none of them was aware of the experimental procedure). The experimental condition included two sessions with visual and acoustic stimuli, respectively. Between the two experimental conditions, there was a 2-min break with Twin 1 (i.e., the subject outside the scanner) relaxing with eyes closed. Data analysis revealed significant brain activation in three regions, namely left orbitofrontal gyrus (during visual condition) and left cingulum and precentral gyrus (during the acoustic condition). Our findings denote emotional connectedness between a pair of monozygotic twins using fMRI. Further studies in larger sample sizes are needed to investigate if this is a generalized and systematic phenomenon or an incidental finding.

Multiparametric Magnetic Resonance Imaging of the Prostate for Tumour Detection and Local Staging: Imaging in 1.5T and Histopathologic Correlation.

PURPOSE: The study sought to prospectively evaluate which technique among T2-weighted images, dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI), diffusion-weighted (DW) MRI, or a combination of the 2, is best suited for prostate cancer detection and local staging. METHODS: Twenty-seven consecutive patients with biopsy-proven adenocarcinoma of the prostate underwent MRI on a 1.5T scanner with a surface phased-array coil prior radical prostatectomy. Combined anatomical and functional imaging was performed with the use of T2-weighted sequences, DCE MRI, and DW MRI. We compared the imaging results with whole mount histopathology. RESULTS: For the multiparametric approach, significantly higher sensitivity values, that is, 53% (95% confidence interval [CI]: 41.0-64.1) were obtained as compared with each modality alone or any combination of the 3 modalities (P < .05). The specificity for this multiparametric approach, being 90.3% (95% CI: 86.3-93.3) was not significantly higher (P < .05) as compared with the values of the combination of T2+DCE MRI, DW+DCE MRI, or DCE MRI alone. Among the 3 techniques, DCE had the best performance for tumour detection in both the peripheral and the transition zone. High negative predictive value rates (>86%) were obtained for both tumour detection and local staging. CONCLUSIONS: The combination of T2-weighted sequences, DCE MRI, and DW MRI yields higher diagnostic performance for tumour detection and local staging than can any of these techniques alone or even any combination of them.

Iron Oxide Nanoparticles as Contrast Agents in Molecular Magnetic Resonance Imaging: Do They Open New Perspectives in Cardiovascular Imaging?

Molecular magnetic resonance imaging has recently emerged as a powerful tool for the detection and assessment of cardiovascular diseases. Contrast agents have an important role in this novel modality because molecular imaging requires highly sensitive, specific, and efficient imaging agents. Iron oxide nanoparticles (IONs) are a new class of contrast agents with unique properties that provide special opportunities in cardiovascular molecular imaging. IONs are captured by macrophages and can be successfully used in the detection and evaluation of atherosclerotic plaques, abdominal aortic aneurysms, and inflammations related to myocardial infarction. The purpose of this review is to provide a brief description of the basic characteristics of IONs, with a special focus on their role as molecular magnetic resonance imaging contrast agents and their cardiovascular applications.

Radiation dose and image noise evaluation in coronary computed tomography angiography (CCTA) using an iterative reconstruction algorithm.

INTRODUCTION: The purpose of this study was to evaluate radiation dose reduction in coronary computerised tomography angiography (CCTA), using a commercially available iterative reconstruction (IR) algorithm as well as the behaviour of the image noise. METHODS: A total cohort of 47 patients underwent CCTA examination on a 64-slice multi-detector CT. They were divided into four groups according to the time when the examination was performed (before or after the installation of iDose) and the acquisition protocol followed (prospective or retrospective electrocardiography-ECG gated). The images acquired with reduced dose settings were reconstructed using two levels (L4 and L6) of the iDose4 algorithm. Image noise was measured in all cases. RESULTS: In retrospective acquisition, images acquired with a 46% lower radiation dose and reconstructed with iDose4 L6 provided noise comparable to that in the full-dose filtered back-projection images. For the prospective acquisition mode, a slight decrease (26%) in radiation dose resulted in noise improvement in low-dose images reconstructed with iDose4 L4 (16% noise removal) and L6 (30% noise removal). CONCLUSIONS: The fact that image quality is improved while radiation exposure is reduced indicates that there is room for a further reduction in exposure settings. Additionally, the combination of iDose4 with prospective acquisition is able to significantly reduce the radiation dose associated with CCTA at values of about 2 mSv and even lower.